In "The Case of the Unknown Stink," students are invited to actively join the tree house detectives as they accept the challenge of trying to find the source of an unpleasant odor that is invading the surrounding neighborhoods. To determine the source of the stink, our detectives learn about the sense of smell: what it is; how humans and animals smell and how wind speed and direction influence the movement of odor. They also learn about how NASA's Atmospheric Science research can help solve the case. While investigating the case, the tree house detectives learn that the source of the "unknown stink" is "right under their very noses."